Nitrogen supplementation of corn silages. 2. Assessing rumen function using fatty acid profiles of bovine milk

• Tipo: Artigo em Revista Científica Internacional
• Data: 2003

Autores

A. Cabrita (Autor) FCUP; Antonio J M Fonseca (Autor) ICBAS; Dewhurst, RJ (Autor) Outra; Gomes, E (Autor) Outra

Revista

Título: Journal of Dairy Science

Vol. 86 Nº 10

Páginas: 4020-4032

ISSN: 0022-0302

Editora: Elsevier

Indexação

ISI Web of Knowledge - 40 Citações

Scopus - 41 Citações

Classificação Científica

CORDIS: Ciências Naturais > Ciências agrárias > Zootecnia

FOS: Ciências agrárias > Ciência animal e dos lacticínios

Outras Informações

ID Authenticus: P-000-E9T

Abstract (EN): The effects of N supplementation strategies on milk fatty acid profiles of dairy cows and their use as a noninvasive technique to diagnose rumen function, and to guide protein feeding decisions on-farm were evaluated in three experiments. Each experiment was designed according to three 3 x 3 Latin squares with 9 Holstein cows receiving total mixed rations based on corn silage. Experiment 1 was designed to study effects of diets with different ratios of effective rumen-degradable protein (ERDP; g) to fermentable metabolizable energy (FME; j) providing, respectively, a large deficiency, a slight deficiency, and a slight excess in relation to the target level of 11 g of ERDP/MJ FME for lactating cows. Experiment 2 evaluated effects of different proportions of quickly and slowly rumen-degradable protein achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea for U0, U5, and U10, respectively). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in rumen by offering the protein-rich concentrate once or twice per day before the meal (corn silage, ryegrass hay, and energy-rich concentrate), or included in the total mixed ration. Milk fatty acid profiles were significantly affected by dietary N and carbohydrate supply. Principal component factor analysis provided a reasonable description of the data, clearly discriminating between fatty acids that are synthesized by different metabolic pathways. Several sources/pathways were distinguished: de novo synthesis in the mammary gland (short- and medium-chain fatty acids), Delta(9)-desaturase activity (monoenoic fatty acids), direct absorption from the blood stream (long-chain fatty acids), and de novo synthesis by the rumen microbial populations (odd-chain fatty acids). Discriminant canonical analysis showed that milk odd-chain fatty acids had a higher ability to discriminate between diets than even-chain fatty acids. The anteiso C-15:0 increased in line with increasing sugar supply, and C-17:0 appears to be a marker of protein deficiency. Additionally, iso C-17:0 and anteiso C-17:0 were associated with the NDF and CP contents of diets. The results suggests that milk odd-chain fatty acids have the potential to be used as a noninvasive technique to assess rumen function in terms of microbial populations, substrates and interactions.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 13